I. Technical Field
The present embodiments generally relate to particle beam irradiation systems for treating ocular tumors.
II. Background
Particle therapy systems for the treatment of ocular tumors use dedicated beam lines for the irradiation of the ocular tumor. Irregularly shaped tumors with awkward configurations near critical structures are well suited for proton beam therapy. Protons have a physical advantage over gamma rays and x-rays when it comes to sparing normal tissues. Protons deposit most of their radiation energy in what is known as the Bragg peak, which occurs at the point of greatest penetration of the protons in tissue. The exact depth to which protons penetrate, and at which the Bragg peak occurs, is dependent on the energy of the proton beam. This energy can be very precisely controlled to place the Bragg peak within a tumor or other tissues that are targeted to receive the radiation dose. Because the protons are absorbed at this point, normal tissues beyond the target receive very little or no radiation.
In order to properly focus these dedicated beam lines, complex equipment for beam shaping and collimation as well as target fixation is utilized. Target fixation is achieved by using a light source in which the patient focuses his or her sight. The position of the pupil of the patient's eye is monitored by a video camera. To allow different incident beam angles, the camera and light source can be rotated around the beam axis, thereby varying the radial position of the eye of the patient. The ocular tumor is then treated with small treatment fields with sharp dose gradients created using collimators made out of a high-z metal which are positioned directly in front of the patient.
When using scanned particle beams for treatment of other portions of the body, the collimators of the particle therapy system might be omitted, thereby allowing the space in front of the patient to be used for automated external imaging devices which improve the clinical work flow. However, this set up does not allow the radiation of small fields with sufficient precision for eye treatment. Moreover, the space used by the automated external imaging devices does not allow the installation of target tracking or fixation devices for the treatment of ocular tumors without interfering with the external imaging capabilities.